The aim of this study was twofold: 1. To study the timing of copulation-solicitation displays (CSD) in female canaries during a natural breeding cycle; 2. To address the question of the adequacy of invasive methods such as oestradiol treatment. Towards these ends, we compared seven oestradiol-implanted and eight control females. Moreover, temporal relationships between reproductive behaviour and plasma concentrations of luteinizing hormone and oestradiol were investigated.
The results showed that: 1. CSD appeared about 3 d before egg laying, after the peak of nest building. The maximum number of CSD was observed at the beginning of egg laying. CSD disappeared when the last egg was laid, at the very beginning of incubation; 2. No significant difference was found between the two groups for any behavioural criterion, particularly CSD. No significant difference appeared between control and oestradiol-treated females for luteinizing hormone concentrations. In contrast, oestradiol-implanted females presented higher levels of oestradiol during nest building and during egg laying, 9–13 d after implantation (median 2.53 and 1.47 ng/ml for implanted females vs 0.57 ng/ml and undetectable levels for controls). Implantation had no effect on the progress of nest building, CSD exhibition, egg laying and incubation. Our results suggest that implantation with oestradiol is not necessary in female canary to obtain CSD since they breed readily in captivity and already have enough oestradiol. The similar results in both groups lead one to question the necessity of oestradiol priming in some female choice experiments.